Mercury type pressure transfer device



April 7, -1953 M. F. MILLER 2,533,744

MERCURY TYPE PRESSURE TRANSFER DEVICE Filed April 18, 1949 2 SHEETS-SHEET l m I 22 Plea-L f Jl 1 ,7 oooh@ o o o 0:00@

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Application April 18, 1949, Serial No. 88,203

(Cl. 'i3-147) (Granted under Title 35, U. S. Code (1952), sec. 266) Claims.

The present invention relates to a pressure .transfer device and more particularly to a device (for, transferring simultaneously multiple pressures from a rotating object to a stationary object, or vice Versa. An object of the invention is the provision of a -device for transferring simultaneously and t without leakage numerous channels of fluids from rrrotating objects to stationary objects.

Another object is to provide a device for trans- .ferring simultaneously at least twenty-four pressures from a rotating object to a stationary oby ject..without appreciably increasing the size of the device. AA yfurtherobject'is to provide a pressure transfer device which will transfer efficiently high pressure differences.

Still another object is to provide a pressure F'transfer device lcapable of transmitting pressure differences higher than those ordinarily encoun- 'teredV in recording pressures on rotating airfoils. A lstill further object of this invention is the :provision of a pressure transfer device capable of operating at speeds up to 6000 revolutions per minute.

A Y Other objects and many attendant advantages of the present invention will be apparent from 4`the following detailed description when taken together with the accompanying drawings 1n 4,.which:

Fig. 1 is a plan View of one form of pressure transfer device according to the present invention.

L Fig. 2 is a sectional view taken along the line L2`2r of Fig. 1 looking in the direction of the arrows.`

Fig. 3 is a sectional view similar to Fig. 2 illustrating another embodiment of the invention.

Fig. 4 shows a front elevational View of a typical impeller of the device of Figs. 1 to 3.

Fig. 5 is a sectional view taken along the line 5-5 of Fig. 4.

Fig. 6 illustrates a single mercury seal between the impeller and stator according to the invention; and

Fig. 7 is a detail of a preferred connection between the impeller and the rotor tube according to the invention.

Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in Fig. 1 a pressure transfer device, generally designated II, connected by any suitable means to a at tank I2 containing mercury, or

any other suitable fluid. Transfer device I I comprises a stator I3 consisting of two halves I4, I5 suitably joined together at one end by means of bearing support I6, cover plate Il and bolts I8 extending through plate I1, support I6 and halves I4, I5 of stator I3. The halves I4, I5 are connected together at the other end by means of bearing member I9 suitably secured to stator I3 such as by additional bolts IB.

Stator I3 has a self-contained water jacket 2| for cooling the stator during the operation of the device, there being suitable passages 22, 22 in stator I3 for permitting the water to flow therethrough from an external source, not shown. Rotatably supported in stator I3 by means of sealed bearings 24, 25 is a rotor shaft 26 which is adapted to be connected by any suitable means, to the rotating object, not shown, whose pressure is to be measured, there being suitable tubes, one of which is shown at 21, extending through a central passage 28 in rotor shaft 2B, each tube being adapted to be connected to a point on the rotating object whose pressure is to be measured.

On an airfoil, for example, under test for pressure conditions at distributed points along the surface thereof, the motor shaft 26 is rigidly coupled by any known means, as by bolting, to the hollow shaft of the airfoil, and the tubes 21 are extended into the airfoil shaft and connected to "manometer tubes embedded in the airfoil surface and extending to a series of distributed test points thereon. Preferably, radially adjacent manometer points are connected to axially adjacent impeller spacings so as not to overload each impeller unit; and in this manner large pressure differences may be summed by the apparatus.

Each tube 21 is preferably made of a metal which Will not react chemically with the mercury, such as stainless steel, and extends to an impeller 29, mounted on shaft 26, through a longitudinal groove 39 in shaft 26, as clearly shown in Fig. 2. The connection between tube 21 and impeller 29 is made airtight by any suitable means, such as silver soldering a tapered fitting to the end of tube 21, coating the fitting with rubber cement and driving the fitting tightly into the aperture 45 in impeller 29. The impellers 29 are each keyed as at 4I to shaft 26 and are pressed tightly against each other by means of shoulder 3| at one end of shaft 2B and a nut 32 at the other end of the shaft, the bearing surfaces being preferably ground and lapped in order to vprovide airtight junctions.

cording to this invention, it can be seen that impeller 29 causes mercury 33 to rotate in a circular chamber and mercury 33 forms a seal around the periphery of impeller 29. The faces of the impeller 29 are provided with radial cut outs 34 in order to provide sufficient traction to rotate the mercury, it being seen in Fig. 4 that alternate cut outs 34 are provided on opposite faces of impeller 29. It has been found that impellers comprising smooth disks or disks with small radial grooves on each face proved to be unsatisfactory to permit pressure transfer at the rotational speeds contemplated.

Impeller 29, according to the invention, will cause mercury 33 to rotate at the periphery thereof when its rotational speed is approximately 350 revolutions per minute, or higher if the spacing between impeller 29 and stator I3, as shown in Fig. 6, is approximately 0.045 inch. It is essential that the sides of impeller 29 near the periphery thereof be smooth in order to prevent turbulence, and that cut outs 34 in the faces of impeller 29 not extend to the outer surface, as shown in Figs. 4 to 6, in order to form a perfect seal.

In operation, when a difference in pressure exists across impeller 29, between points 35 and 3G in Fig. 6, rotating mercury 33 assumes the shape shown in Fig. 6, the centrifugal force of the mercury balancing the force caused by the dif-V 5;.

ference in pressure and thereby forming a seal. When the force on mercury 33 caused by the difference in pressure exceeds the centrifugal force, the gas or liquid in tube 2l' will leak from one side of the impeller to the other thereby disrupting the operation of the device. However, because the specific gravity of mercury is high, it has been found that the diameter of impeller 29 need not exceed three inches to provide for sufficient centrifugal force for the transfer of airfoil pressures, if cut outs 34 are of approximately 0.625 inch in order to provide sufficient traction for mercury 33.

Tank I2 for mercury 33 is of relatively large volume so as to serve as a reservoir forfthe excess mercury during operation, and to assure equal distribution throughout the various cells. The passage from tank I2 to stator I 3 is through openings 23 While the level of the tank is between openings 23 and the lower surfaces of the central opening in wall members 49 in order to prevent the mercury from passing over the openings in the wall members 48 and into the spacing between members 43 and bearings 24 or 25.

Under initial static conditions, mercury 33 from tank I2 enters stator I3 through openings 23 and is distributed equally throughout the various cells by means of vents or openings 3'! in the radial partitions or fins 41 of stator I3. When the impeller rotates, the mercury is carried around the impeller chamber, additional mercury owing into the chamber from the tank to supply the added amount required to balance the tank and impeller pressures. When impeller-rotation ceases, the excess mercury flows back to the tank. In this manner, adequate mercury supply for the casing is assured without ooding of the shaft bearings.

It will Vbe apparent that the device EI will not only measure simultaneously a plurality of pressures, but that a large pressure differential, such as between the extremes of a rotating airfoil, can be readily reproduced, since device II will Yln other gwords, although the pressure 4 differential between extreme cells may be exceedingly great, the pressure differential across each cell will be sufficiently small so that it can be equalized by the centrifugal force. In this manner the pressure distribution along the rotating object is readily obtainable, and, by a summation of the individual pressure differences across each cell, the total pressure differential can be measured.

The pressure transfer from each cell to external indicators, vnot shown, is made through openings in the inner ends of the upper portions of fins 4l; as shown in Fig. 2 and through tubes 3S extending into fins 4l, it being understood that any suitable pressure measuring device may be used as an indicator.

It is essential that there be a smooth juncture between halves I4, I5 of stator I3, if leaks around impellers 29 are to be prevented during operation of the device. Experimentation has demonstrated that the transfer device of Figs. l and 2 will perform transfers satisfactorily for rotational speeds up to approximately 4000 revolutions per minute, there being a leakage of mercury out of stator I3, where halves I4, I5 join, at speeds greater than 4000 revolutions per minute.

Referring now to Fig. 3, there is shown an improved embodiment of the present invention which is capable of satisfactorily operating at least as high as 6600 revolutions per minute, and which does not require the difficult machining and finishing of the two halvesV I, I5 of the stator I3 of Figs. 1 and 2. As shown in Fig. 3, stator I3 comprises a plurality of circular rings 5I, each having a gro-ove on one side into which is inserted a sealing ring 42 of suitable material, such as neoprene. When rings 5I are pressed tightly against one another in assembly, a highly effective seal is formed which permits operation, without leakage, at very high speeds. A similar arrangement of sealing rings 42 was used for impellers 29 of Fig. 3 in order to avoid the necessity of lapped surfaces, as in the embodiment of Figs. l and 2.

To avoid the use of solder and to form a more perfect seal between tubes 2'! and impellers 29, a form of neoprene seal, as clearly shown in Fig. 7, was utilized. After tubes 21 were inserted in their associated impellers 29 a section of neoprene tubing 43 was placed thereover and a screw 34 was forced against tubing 43 to form an excellent seal. A similar connection, not shown,

' was utilized between disks 4I of stator I3 and tubes 38. The remaining parts of the device of Fig. 3 correspond to those of the device of Figs. l and 2, and reference is made to the earlier description thereof for the operation of this improved embodiment.

Although the devices illustrated have been primarily designed for transferring only twentyfour pressures simultaneously, it is clear that the number of pressure channels may be increased considerably with only a relatively small increase in length of the device, particularly able attention must be given to the cooling system where operation at speed higher than 6000 revolutions per minute are contemplated.

Various modifications are contemplated and may obviously be resorted to by those skilled in the art without departing from the spirit land scope of the invention, as hereinafter defined by the appended claims, as only preferred embodiments thereof have been disclosed.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental `purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. In a device for determining the ypressure distribution on the surf-ace of Va rotating object, a rotatable shaft, a plurality of impellers mounted on said shaft and extending radially outwardly thereof; each of said impellers having a plurality of radial cut outs on at least `one of the surfaces thereof terminating short of the impeller periphery to form a smooth annulus, a Iplurality of tubes each extending longitudinally along said shaft and terminating at one end in Ithe spacing between adjacent impellers, the other end of each of said tubes being adapted to be connected to a point on said obj-ect, Ia casing enclosing said shaft and impellers and having a plurality of radial fins each extending into one of said spacings, said casing being `adapted to receive fluid means responsive to the rotation of said `shaft for forming a seal between each impeller and its associated n, and duct means extending from the inner end of each of said ns outwardly of said casing.

2. In a device for determining the pressure distribution on the surf-ace of -a rotating object, ia rotatable shaft having a plurality of disc impellers mounted transversely thereon, each lof said impellers, having a plurality of radial cut outs on the surface thereof, a plurality of tubes extending along said shaft each terminating at one end in separate spacings between adjacent impellers, the other end of each of said tubes being adapted to be connected to a point on the surface of said object, a casing enclosing -said shaft and impellers and having a plurality of radial ns each projecting into said spacing, sai-d casing being adapted to receive liquid sealing means between said fins and im-peller, duct means extending from the inner ends of each of 'said ns to without said casing, and a liquid containing tank mounted below the level `of said shaft and connected for liquid flow to and from said casing for holding the liquid level of said Isealing means below said shaft when the yshaft is stationary.

3. In Ia device for determining the pressure distribution on the surface of va rotating object, the combination comprising la rotatable shaft, 'a plurality of disc impellers mounted transversely on said shaft each inclu-ding a radially outwardly extending flange having cut outs in the surface thereof terminating short of the impeller periphery, sealing elements between each pair of impellers, a plurality of tubes ext-ending longitudinally along said shaft and each terminating at one end in the spacing between adjacent impeller flanges, a stationary casing surrounding said shaft and said impellers, a plurality of annular members coaxial with said shaft and positioned between said shaft and said casing, sealing elements between said members, each of said members having :a n extending inwardly into said spacing, duid sealing means in said ycasing for forming a seal between each of said fins and its associated flange, and duct means extending from the inner end of each of said ns to without said casing, the other end of said tubes being adapted for connections to pressure devices on 4said rotating object.

4. The combination according to claim 1, and openings in the outer end of each of said fins for equalizin'g the distribution of said uid sealing means.

5. In a device for determining the ypressure distribution on the surface of a rotating object, a rotatable shaft, a plurality of impellers mounted on said shaft and extending radially outwardly thereof; each of said impellers having a `plurality of radial cut-outs on the surface thereof, a plurality of tubes each extending longitudinally 'along said shaft and terminating iat one end in separate -spacings between adjacent impellers, the other end of each of said tubes being `adapted to be connected to a point on said object, a casing enclosing said shaft and havingr a plurality of radial ns each extending into said "spacing, fluid means responsive to the rotation of said shaft for forming a seal between each impeller 'and its associated fin, vduct means extending from the inner end of each of said iins outwardly of said casing, and a ui-d reservoir for supplying uid to said fluid means, said reservoir between positioned at Ia level such that innormal operation fluid is supplied to said reservoir under static conditions and fluid is supplied to said casing when said shaft is in rotation.

MASON F. MILLER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,044,317 Wemdt Nov. 12, 1912 1,289,903 Pogue Dec. 31, 1918 1,395,448 Moore Nov. 1, 1921 1,405,177 Zahm Jan. 31, 1922 2,038,091 Wheeler Apr. 21, 1936 2,429,481 Mohr et al Oct. 21. 1947 

